Both thought experiments essentially begin by assuming their own conclusions and using them as evidence. Particularly dumb stuff, a hallmark of mediocre philosophy. The very fact they could reach opposite conclusions with virtually the same experiment shines a bad light on them both.

It wouldn't prove anything - all you need is some part of a brain that creates a delayed feedback loop and you don't need external senses for self-stimulating thought, and yet there is no soul needed in that scenario.

Yes, but the more disturbing point is this: under most premises that are reasonable in the context of physics, if we break experience down as sequences of single thoughts, than statistically a single thought should be more likely to arise from Boltzmann brains than the ones that we know. Or (more likely IMO) we haven't quite figured out the statistics here yet.